The primary focus of the project is a systematic, comprehensive assessment of behavioral consequences of sleep apnea in children and adolescents. The project will also examine specific etiologic parameters bearing on the development of sleep apnea. Four approaches will be used. In Study 1,80 children with adenotonsillar enlargement in whom surgery has been recommended will receive basal assessments of sleep, breathing, and waking function. This group is prescreened to include 40 children with and 40 without sleep apnea. A 48-hour behavioral protocol includes two nocturnal sleep/breathing recordings, daytime testing of sleepiness, neuropsychological testing (along the dimensions of intelligence/achievement, attention/impulse control, learning/memory, response speed/productivity, and problem solving/mental control); pubertal status (Tanner staging); and cephalometrics. Findings are compared in children with and without sleep apnea. Study 2 examines treatment effects. Children in the Study 1 groups are re- evaluated after surgery using a 36-hour abbreviated behavioral protocol, along with upper airway assessments. Data are compared between those children who did and did not have sleep apnea before surgery. Findings from the treatment study will indicate the reversibility of deficits in waking function resulting from sleep apnea. Study 3 uses experimental approaches in normal older adolescents to examine functional issues more directly. Ten subjects each are randomly assigned to a control condition or to undergo sleep fragmentation resulting form one of three experimental procedures: interruptions at the rate of 10/hour for 3 nights or 30/hour for 3 nights; or, interruptions caused by nasal obstruction for 3 nights. This study compares the impact on waling function of sleep fragmentation with and without disturbed breathing. Cumulative effects of these procedures on walking function are also assessed. In study 4, nasal obstruction challenge is used to assess whether growth and sex interact with airway structure to alter an individual's vulnerability to develop sleep apnea. Relationships between cephalometric measures and sleep apnea induced by nasal obstruction in groups of 25 normal subjects-- adolescent boys and girls and young adult men and women-- are compared. In summary, this project examines in children and adolescents the risks of developing sleep apnea, the behavioral consequences of sleep apnea, the etiology of sleep apnea, the effects of treatment of sleep apnea, and the contributions of sleep fragmentation and upper airway obstruction in producing the behavioral deficits.